function [V lambda] = PCA_notrick(allGPAShape)
estShape = getProcrusteMeanShape(allGPAShape);
[a n N] = size(allGPAShape);
S = zeros(n*2,2*n);
for i=1:N
    dx_i = [allGPAShape(1,:,i)-estShape(1,:) allGPAShape(2,:,i)-estShape(2,:)];
    S = S + dx_i'*dx_i;
end

S =  1/(N-1)*S;

[V, lambda] = eig(S);
lambda = (diag(lambda));
